SAE 750381, pages 4 and 12, describes a four-speed transmission which consists of a Simpson-type planetary gear set followed by a simple planet set arrayed thereafter, and which has two clutches and three brakes. A hydrodynamic unit is provided ahead of the transmission.
Transmissions of this type with a Simpson-type planetary gear set as a three-speed transmission unit have proven themselves particularly in transmissions to be shifted automatically.
However, their construction is complicated and the cost of manufacture is high. The overall length of the transmission is not satisfactory, and the positions of the clutches and brakes are not optimal with respect to the planetary sets.